The contamination of drinking water sources with organic impurities, especially in industrialized areas, is a major environmental concern. Such impurities commonly include chlorinated hydrocarbons as well as aromatics such as benzene. A common method which addresses this problem is to pass the contaminated water through beds of activated carbon, which removes the impurities by surface adsorption. Other methods of purification which have been developed include distillation, extraction, and membrane separation.
Air contamination with toxic organic chemicals is another health hazard which commands attention. Air is also purified in industrial operations requiring "clean rooms". The use of filtration and adsorption techniques is common in addressing air purification problems.
In addition to activated carbon a variety of polymeric adsorbents have been developed and used successfully for water purification. Fritz and Tateda, Analytical Chemistry. Volume 40, pages 2115-2119 (1968) disclose products of Rohm and Haas which are marketed under the Amberlite trademark. For example. A-26 is described as a macroreticular ion exchange resin. Other products of this type are described by Paleos, J. Colloid and Interface Science. Volume 31. page 7-18 (1969), including the Amberlite species designated as XAD-2,4,7, and 8. The product literature of Rohm and Haas describes these products as forms of cross-linked polystyrene or cross-linked poly(methylmethacrylate) with and without functional groups. It is stated that these resins adsorb polar solvents from non-polar solvents based upon the surface properties of the insoluble beads of the porous polymer and, therefore, are capable of removing contaminants from aqueous systems. The method of operation of these products in removing the contaminants from water is through adsorption of the contaminants on the surface of the polymer and polymer efficiency is increased by increasing its surface area.
The concentration of organic vapors in air space, such as in a storage vessel can be reduced by absorption using particulate vulcanized rubber as the absorbing medium, according to U.S. Pat. No. 4,728,383, Snyder (1988). U.S. Pat. No. 4,764,282, Snyder (1988) discloses using ground rubber to absorb toxic organic chemicals for transportation and incineration.
Other methods of water purification involve the use of membranes, also known as pervaporation. Aptel et al., J. Membrane Science, Volume 1, pages 271-287 (1976) disclose that positive azeotropic liquid systems, such as water and alcohol, are separated by pervaporation through a membrane of poly(tetrafluoroethylene) grafted with N-vinylpyrrolidone, enhanced with a temperature gradient driving force. The purification of wastewater containing organic materials is discussed by Leeper et al., "Membrane Technology and Applications: An Assessment", contract number AC07-761D01570; U.S. Department of Energy (Feb. 1989). This report describes the treatment of water contaminated with oils by energy intensive distillation, air flotation or with ultrafiltration, and also notes that phenol containing water systems have been purified using membrane separation techniques. Cabasso et al., J. Polymer Science; Polymer Letters to the Editor, Volume 23, pages 577-581 (1985), disclose sulfonated polyethylene ion exchange membranes for the separation of alcohol-water mixtures.
Masuda et al., Macromolecules. Volume 18, page 841-845 (1985) disclose that the monomer 1-(trimethylsilyl)-1-propyne can be polymerized by catalysts based upon pentahalides of niobium or tantalum and that the high molecular weight polymer thus formed makes tough films on casting. Masuda et al., Advances in Polymer Science, Volume 81, pages 121-165 (1986) also describe the synthesis of substituted polyacetylenes, including poly(trialkylsilylpropynes), and state that some of the polymers are useful as membranes for the separation of gases and liquids. A membrane formed with poly[1-(trimethylsilyl)-1-propyne] was disclosed as useful in pervaporation of ethanol-water mixtures and it is stated that such a membrane is ethanol-permselective. Such separation is further discussed by Masuda et al., Polymer Journal, Volume 18, pages 565-567 (1986) and Masuda et al., J. Polymer Science. Part A, Polymer Chemistry, Volume 25, pages 1353-1362 (1987), who describe this polymer as having extremely high oxygen permeability.
In pervaporation membrane separation processes, the more permeable component of a liquid mixture passes through the membrane at a faster rate relative to the feed composition, thus yielding a separation of components. Poly[1-(trimethylsilyl)-1-propyne)](PTMSP), is of particular interest for pervaporation applications due to its very high diffusion coefficient and the ability to transport organic molecules faster than water. Permeation rate is a product of the diffusion coefficient and solubility constant. For separation of organic trace impurities from water, the high solubility factor ratio of organics/water yields a favorable separation of organics versus water through a PTMSP membrane. This favorable separation is diminished however, by the unfavorable diffusion coefficient ratio, where water (as a smaller molecule) has a higher value than the organics, thus yielding a decrease in the overall permeability separation factor compared to the solubility factor.